[PATCH v8 15/18] scsi: scsi_debug: Support host tagset

John Garry
2020-08-19T15:27:36Z

When host_max_queue is set (> 0), set the Scsi_Host.host_tagset such that
blk-mq will use a hostwide tagset over all SCSI host submission queues.

This means that we may expose all submission queues and always use the hwq
chosen by blk-mq.

And since if sdebug_host_max_queue is set, sdebug_max_queue is fixed to the
same value, we can simplify how sdebug_driver_template.can_queue is set.

Signed-off-by: John Garry <john.garry@huawei.com>
---
drivers/scsi/scsi_debug.c | 28 ++++++++++------------------
1 file changed, 10 insertions(+), 18 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 064ed680c053..4238baa2b34b 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -4698,19 +4698,14 @@ static int resp_rwp_zone(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
static struct sdebug_queue *get_queue(struct scsi_cmnd *cmnd)
{
u16 hwq;
+ u32 tag = blk_mq_unique_tag(cmnd->request);

- if (sdebug_host_max_queue) {
- /* Provide a simple method to choose the hwq */
- hwq = smp_processor_id() % submit_queues;
- } else {
- u32 tag = blk_mq_unique_tag(cmnd->request);
+ hwq = blk_mq_unique_tag_to_hwq(tag);

- hwq = blk_mq_unique_tag_to_hwq(tag);
+ pr_debug("tag=%#x, hwq=%d\n", tag, hwq);
+ if (WARN_ON_ONCE(hwq >= submit_queues))
+ hwq = 0;

- pr_debug("tag=%#x, hwq=%d\n", tag, hwq);
- if (WARN_ON_ONCE(hwq >= submit_queues))
- hwq = 0;
- }
return sdebug_q_arr + hwq;
}

@@ -7347,10 +7342,7 @@ static int sdebug_driver_probe(struct device *dev)

sdbg_host = to_sdebug_host(dev);

- if (sdebug_host_max_queue)
- sdebug_driver_template.can_queue = sdebug_host_max_queue;
- else
- sdebug_driver_template.can_queue = sdebug_max_queue;
+ sdebug_driver_template.can_queue = sdebug_max_queue;
if (!sdebug_clustering)
sdebug_driver_template.dma_boundary = PAGE_SIZE - 1;

@@ -7367,11 +7359,11 @@ static int sdebug_driver_probe(struct device *dev)
}
/*
* Decide whether to tell scsi subsystem that we want mq. The
- * following should give the same answer for each host. If the host
- * has a limit of hostwide max commands, then do not set.
+ * following should give the same answer for each host.
*/
- if (!sdebug_host_max_queue)
- hpnt->nr_hw_queues = submit_queues;
+ hpnt->nr_hw_queues = submit_queues;
+ if (sdebug_host_max_queue)
+ hpnt->host_tagset = 1;

sdbg_host->shost = hpnt;
*((struct sdebug_host_info **)hpnt->hostdata) = sdbg_host;
--
2.26.2